FlashDevelop is the premiere open-source Adobe Flash ActionScript 3 Editor, and can be used to build websites and applications for desktop and mobile, that target Flash Player 9+ or Adobe AIR with ActionScript 3.

FlashDevelop tightly integrates with AS3 compilers and debuggers:

Supported compilers

• Compile via Adobe Flash IDE
• Compile via Adobe Flex SDK
  • Flash Player (web)
  • AIR Desktop
  • AIR Mobile
• Batch files for AIR Developer Tool
  • Package app for Android, iOS
  • Package native app for Windows, Mac OS X

Project templates for AS3

• Flash Player (web)
• AIR Desktop
• AIR Mobile

Compiling via Flex SDK

• Project build config GUI (Project > Properties)
• Auto generation of build XML files based on config
• Debug and Release mode configurations
• Incremental compilation (faster complies 2nd time onwards)
• ASC 2.0 Support (Adobe "Falcon" compiler, generates faster SWFs)
• Build errors show in Errors panel (double click error to navigate)
• Multiple SDKs can be registered with FD4, and easily switched

Debugging via Flex SDK

• Pause/resume support, Stepping (step over, step in, step out)
• Assign breakpoints before and during debugging
• View all breakpoints (panel), remove all breakpoints
• Roll over variable to show live value (when debugging and paused)
• Show live values of variables in tree format
• Auto break on error (highlights the crashed line)
• Call stack when stepping (double click callstack item to navigate)
• Profiler panel with Memory usage and Live object count

SDK Management

• Auto downloads needed SDKs (Flash, Haxe) during installation
• App Manager to view/download latest SDKs (Tools > Install Software)

FlashDevelop helps you work with your AS3 projects:

Code refactoring

• Rename class or member
• Find all references
• Extract method
• Extract local variable
• Code formatter (options in "CodeFormatter" page)

Code completion, or "IntelliSense"

• Platform API shows in IntelliSense (based on Flash Player version)
• User classes, methods, and variables list in IntelliSense
• Only applicable events list when adding/removing listeners
• SWC library classes and code appear in IntelliSense
• Typed vectors show class members
• Typed arrays : var points:/*Point*/Array
• Manually open list : Ctrl+Spacebar or Ctrl+Alt+Spacebar (search all classes)

Code information tooltips

• ASDoc comments show when calling functions, or accessing classes/members
• ASDoc comments show on rolling over a member/function/class
• ASDoc comments show for the current argument, when Ctrl+Shift+Spacebar pressed

Code generation

• Generate getter/setter from var
• Generate vars from function arguments
• Generate function from unknown identifier
• Promote local var to class var

Code folding

• Functions, classes and namespaces can be expanded/collapsed
• Regions using //{ and //} syntax
• Collapse/Expand All (collapses functions but not regions)
• Collapse/Expand Regions (collapses everything including regions)

Code navigation

• Navigate to class definition (place cursor on class, press F4)
• Navigate to function/var definition (place cursor on member, press F4)
• Navigate back (press Shift+F4)

Code snippets

• Insert snippet from snippet library, auto placement of cursor
• Snippet library GUI, ability to add/edit/delete snippets

Syntax coloring